Tiresias was a Greek/Roman prophet who came from Thebes. He figures into several stories from Greek and Roman mythology.

One of the more amusing ones occured when he was walking down the road one day, and he saw two snakes having sex. For one reason or another, he took his walking stick and thrashed them badly. The Gods happened to notice this, and, as punishment, turned him into a woman. So he went around as a woman for a while. Seven years later, he saw two snakes lying side by side, and this time he used his walking stick to make them come together. This caused him to be turned back into a man. Later on, Zeus and Hera were having an argument about who has a better orgasm during sex. Remembering that Tiresias had been both a man and a woman, they decided to ask him. Tiresias replied that a woman's orgasm is nine times better.

The loser of the argument between Zeus and Hera struck Tresias with a lightning bolt, which blinded him. As compensation, the winning party gave him the ability to foresee the future.

Tiresias is seen again later on in the story of Odysseus/Ulysses, where he acts as a seer.

Tiresias also makes an appearance in Oedipus Rex to inform King Oedipus that the current troubles in his kingdom are due to a past blasphemy against the Gods.

He only reveals the nature of this blashpemy in oblique terms, letting Oedipus find out all the nasty details himself later in the play.

Teiresias was

a) The Blind Seer of Thebes, who, depending on which myth you're reading, was either blinded when young by Athena (the patron goddess of Athens) for seeing her naked whilst bathing, then given the gift of prophesy when she relented after Teiresias' mother pleaded.

The other (more interesting one in my reckoning) claims the he saw two snakes coupling, and was turned into a woman, until he saw the same two snakes coupling. After this experience he was called upon as an arbiter to an argument between Zeus and Hera, about who got the most pleasure from sex. Teiresias claimed women get '9 or 10 times more' pleasure. This statement annoyed Hera so she blinded him, but won Zeus the argument, so he gave him the gift of prophesy.

He was a follower of Dionysus, the god of wine and vines and being very pissed, (top god to worship in my book) for a while and famously warned the Pentheus not to cross Dionysus,advice which was not heeded, leading to the death of Pentheus. He also predicted the greatness of Hercules (aka Heracles in some texts), and revealed the fact that Oedipus had commited patricide

or

b) My online persona, a shortsighted, know-it-all, who drinks too much ...